Polymeric fibers, such as nanofibers, have a broad array of uses including use as catalytic substrates, photonics, filtration, protective clothing, cell scaffolding, drug delivery and wound healing. Structures prepared using nanofibers are the best candidates for tissue engineering for, e.g., orthopedic, muscular, vascular and neural prostheses, and regenerative medicine due to their high surface to mass ratio, high porosity for, e.g., breathability, encapsulation of active substances, and fiber alignment, and because they can be easily wound into different shapes (Madurantakam, et al. (2009) Nanomedicine 4:193-206; Madurantakam, P. A., et al. (2009) Biomaterials 30(29):5456-5464; Xie, et al. (2008) Macromolecular Rapid Communications 29:1775-1792).
The most common process for fabricating nanofibers is electrospinning. Briefly, electrospinning is a process that uses high voltage to create an electric field between a droplet of polymer solution at the tip of a needle and a collector plate. One electrode of the voltage source is placed into the solution and the other is connected to the collector. This creates an electrostatic force. As the voltage is increased, the electric field intensifies causing a force to build up on the pendant drop of polymer solution at the tip of the needle. This force acts in a direction opposing the surface tension of the drop. The increasing electrostatic force causes the drop to elongate forming a conical shape known as a Taylor cone. When the electrostatic force overcomes the surface tension of the drop, a charged, continuous jet of solution is ejected from the cone. The jet of solution accelerates towards the collector, whipping and bending wildly. As the solution moves away from the needle and toward the collector, the jet rapidly thins and dries as the solvent evaporates. On the surface of the grounded collector, a nonwoven mat of randomly oriented solid nanofibers is deposited (Zufan (2005) Final RET Report; Xie, J. W. et al. (2008) Macromolecular Rapid Communications 29(22):1775-1792; Reneker, D. H., et al. (2007) Advances in Applied Mechanics 41:43-195; Dzenis, Y. (2004) Science 304(5679):1917-1919; Rutledge, G. C. and Yu, J. H. (2007) “Electrospinning” In Encyclopedia of Polymer Science and Technology, John Wiley & Sons: New Jersey; Krogman, K. C., et al. (2009) Nature Materials 8(6):512-518; Pham, Q. P., et al. (2006) Tissue Engineering 12(5):1197-1211; Boland, E. D., et al. (2001) Journal of Macromolecular Science-Pure and Applied Chemistry 38(12):1231-1243; Teo, W. E. and Ramakrishna, S. (2006) Nanotechnology 17(14):R89-R106; Li, D.; Xia, Y. N. (2004) Advanced Materials 16(14):1151-1170; Greiner, A. and Wendorff, J. H. (2007) Angewandte Chemie-International Edition 46(30):5670-5703).
However there are multiple drawbacks associated with electrospinning, such as the requirement for a high voltage electrical field, low production rate, the requirement for precise solution conductivity, and the need for additional devices for producing aligned fiber structures (Lia and Xia (2004) Advanced Materials 16:1151-1170; Weitz, et al. (2008) Nano Letters 8:1187-1191; Arumuganathar, S, and Jayasinghe, S, N. (2008) Biomacromolecules 9(3):759-766).
Accordingly, there is a need in the art for improved methods and devices for the fabrication of polymeric fibers, such as nanofibers.